From 49920d28781dcced10cd30cb9a938e7d045a1c94 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 12 Dec 2016 16:44:50 -0800 Subject: mm: make transparent hugepage size public Test programs want to know the size of a transparent hugepage. While it is commonly the same as the size of a hugetlbfs page (shown as Hugepagesize in /proc/meminfo), that is not always so: powerpc implements transparent hugepages in a different way from hugetlbfs pages, so it's coincidence when their sizes are the same; and x86 and others can support more than one hugetlbfs page size. Add /sys/kernel/mm/transparent_hugepage/hpage_pmd_size to show the THP size in bytes - it's the same for Anonymous and Shmem hugepages. Call it hpage_pmd_size (after HPAGE_PMD_SIZE) rather than hpage_size, in case some transparent support for pud and pgd pages is added later. Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1612052200290.13021@eggly.anvils Signed-off-by: Hugh Dickins Acked-by: Michal Hocko Acked-by: Vlastimil Babka Cc: Greg Thelen Cc: David Rientjes Cc: "Kirill A. Shutemov" Cc: Andrea Arcangeli Cc: "Aneesh Kumar K.V" Cc: Dave Hansen Cc: Dan Williams Cc: Jan Kara Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/vm/transhuge.txt | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'Documentation') diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt index 2ec6adb5a4ce..c4171e4519c2 100644 --- a/Documentation/vm/transhuge.txt +++ b/Documentation/vm/transhuge.txt @@ -136,6 +136,11 @@ or enable it back by writing 1: echo 0 >/sys/kernel/mm/transparent_hugepage/use_zero_page echo 1 >/sys/kernel/mm/transparent_hugepage/use_zero_page +Some userspace (such as a test program, or an optimized memory allocation +library) may want to know the size (in bytes) of a transparent hugepage: + +cat /sys/kernel/mm/transparent_hugepage/hpage_pmd_size + khugepaged will be automatically started when transparent_hugepage/enabled is set to "always" or "madvise, and it'll be automatically shutdown if it's set to "never". -- cgit v1.2.3